The world of microbes is the topic of this essay and explanations on how important they are for modern community. Microbes can for example obtain energy for growth and produced microbial biomass that contains a large percentage of high grade protein. They can also by a fermentive pathway in the metabolism of glucose, produced ethanol. Utilization of microbes is a possible solution of some environmental issues that are hazardous for life on earth. The working process of metabolism in microbes is explained along with the difference between fermentation and respiration. Biomass is essential for various reasons. In this essay the forms of biomass are explained along with how it is formed and utilized.